Swallowing is a complex sensorimotor function that serves the dual functions of transporting material from the mouth to the stomach while protecting the respiratory tract from foreign material. Swallowing involves four stages: the oral preparatory, oral, pharyngeal and esophageal stages. While the oral preparatory and oral stages are under voluntary control, with contributions from the cerebral cortex, the pharyngeal and esophageal stages are autonomic, being controlled by a brainstem network. The pharyngeal stage is triggered when an appropriate pattern of sensory stimulus excites sensory receptors within the oral cavity, oropharynx, and/or pharynx.
Dysphagia, or swallowing impairment, occurs in a number of common diseases and conditions including stroke, cerebral palsy, head and neck cancer, and Parkinson's disease. Dysphagia may affect any or several of the stages of swallowing. For example, a common swallowing abnormality in dysphagia is reduced, or delayed, triggering of the pharyngeal stage of swallowing. As a result, individuals with dysphagia often swallow less frequently when compared with healthy individuals. In addition, when swallowing is performed, the swallow may be slow and/or weak, thus placing the individual at risk of reduced nutritional intake or entry of foreign material into the respiratory tract.
Dysphagia also may result from a lack of saliva, called xerostomia. Xerostomia and associated swallowing impairment occurs in a number of patient diagnostic groups including persons who have undergone radiation therapy in the region of the salivary glands for treatment of cancer of the head or neck, persons with certain systemic conditions, e.g., Sjogren's syndrome, and persons taking medications that reduce salivary flow. When experiencing dysphagia following radiation therapy, patients may perceive their mouths to be even dryer than objective measures of saliva indicate. Unfortunately, the severity of dysphagia is correlated with the degree of perceived mouth dryness. Therefore, both dry mouth and the perception of dry mouth may be problems for patients who have undergone radiation therapy of the head and neck. In addition to the association between dry mouth and dysphagia, dry mouth is unpleasant to the patient, thereby reducing the quality of life.
A variety of stimulus modalities have been applied in attempts to elicit or facilitate swallowing, including electrical stimulation of the pharynx, neck or laryngeal musculature, thermal stimulation of the faucial pillars, modification of diet, exercises, postural adjustments and the use of gustatory stimuli, such as a sour bolus, or combinations thereof. Air-pulse trains also have been considered as a stimulus that may facilitate the pharyngeal swallow. Some devices have been suggested for delivering such air-pulse trains, as disclosed for example in US Patent Publication No. 2010/0016908, published Jan. 21, 2010, the entire disclosure of which is hereby incorporated herein by reference. Air pulse trains are directed to the oral cavity by way of an oral device, which is positioned and secured through various devices. For example, the '908 publication describes, in one embodiment, an “over-the-ear” oral device configured such that the flexible tubing that delivers the air pulse trains wraps around the ears of the user.